The Way West — Richard T. Stevens

One night, everything changed. It wasn't guns or bombs. It wasn't tanks and artillery that killed. It was inevitable. A virus either mutated or was created that had no antidote, and it spread worldwide. As days turned into weeks, and then into months, the virus showed no signs of abating. Entire countries were dying or had died. Civilization didn't go out with a bang, as many thought it would, it died with a whimper. Follow an average young lady along, in the third book of the "Tales of New Hope" series, as she goes from surviving in a St. Louis suburb, to walking the Oregon Trail in search of a brighter future.